first ride eric gorr 2002 cr250 porting and head mods

[john stu]

ok yesterday was the first ride seince i had eric gorr do his thing to my cyl and head a asked for some more bottom with out to much of a loss in top end power and thats what i got.the power came on a little sooner pulled stronger and for a longer time, the powerband seemed wider with only the slightest and i mean slightest loss in over rev.it wasn't a huge difference but it was very noticable
and i honstly don't belive you can make a difference like that any other way besides porting and head mods.with pipes ect you always loose somewere else and the difference is always minamul.so far best $150 i spent on the bike.(bigger improvement than when i did a pipe and silincer and they cost more and you can wreck them when you just fall over)also for some reason the bike seemed to run better it didn't want to load the plug up so much.the mods eric did to my engine made it feel like it should have when i bought it from honda thanks eric. ps the bike was set up for race fuel :moon:

 

[Rich Rohrich]

John - If you are running race fuel you should be able to lean the main jet out enough to raise the exhaust temperature and get most of over-rev you are looking for. The improved scavenging will allow you to run leaner without losing performance or reliability. Pump fuel is to unpredictable to push it this way though.

 

[john stu]

i am going to try leaning it out as soon as it warms up here. i am confused though i thought a slightly rich mixture would give more over rev and a slightly lean mix would give better throttle responce

 

[Rich Rohrich]

Pipe tuning is temperature dependent and in this case it is being influenced by two conflicting combustion related temperature after-effects.

If you run it too rich you are lowering the combustion chamber temps and to some degree the exhaust gas temperature. Lower exhaust gas temps cause the pipe to tune at a lower rpm.

The other side of the coin is, the slower combustion speeds that come with rich mixtures will raise the exhaust gas temps a bit because the peak pressures and temps occur later in the cycle, similar to what happens when you retard the ignition timing. This causes the pipe to tune at a higher rpm.

Which one has the greater influence? I've found it to be engine dependent so you won't know for sure without testing.

FWIW, my personal experience says running it lean enough to have it just flirting with trace knock will pull the hardest and the longest.

Let us know what you find on your engine. :thumb:

 

[Faded]

Please excuse me for butting in, but while we are on the topic of jetting ported 02 CRs I have a few questions.

I'm trying to get my 265 dialed in, and I've read Erics book on the ride and feel, but in there he states that "If the engine is slow to respond and bogs (engine makes a booooowah sound) then the carb jetting is too lean" and "If the carb jetting is too rich, then the engine will make a crackling sound..." I think that my jetting is too rich, but it bogs and "boooooowahs" (mostly going from 1/8 to WFO) indicating that it's lean. I only say I'm rich because other stock 02s in my area are running needles that are 3 steps leaner than mine. How would you describe the crackling sound that indicates a rich mixture? I would like to be picking up some jets and experimenting this weekend to try and get a little closer, but now I'm not sure if I sould buy leaner or richer. Sorry for the general jetting post.

 

[john stu]

rich that is very interesting i will be trying some jetting soon i'll post what i find.and to faded, when i tryed a too small of a pilot jet (too lean) my bike boged when the throttle was opened very quickly from closed to wide open so if your bike is bogging you are probably lean somewhere but that doesn't mean you are lean on the needle you might be rich like everbody else is and you could still be lean on needle clip postion or pilot and air screw or even the main you will have to give some other jets a try to find out what works best

 

[motometal]

which needle jet are you using, Stock?

also, a couple off the wall long shots:

are you sure your power valve is operating properly?

carb vent hoses ok/not plugged? (this is unlikely to be the problem but is a highly neglected item)

 

[Faded]

Motometal,

Needle Jet (nozzle) is down one size, an S-8 from an S-9. Jet needle is BEY-3074 (this is 2-3 sizes rich compared to others I've talked to). Power valve is operating correctly, vent hoses are clear of any debris. I played with the airscrew a lot this Sat. and went from 1-3/4 out to 1-1/8 and it cured most of my problem! :thumb: I still need to work on needle size and my main jet.

Thanks for the possible problem areas, it was a good idea to check those as well.

 

[motometal]

sounds like you are getting closer. I wouldn't have mentioned the power valve if you hadn't had the engine work done. The power valve can cause some weird symptoms if it isn't working right. I once got an RM engine back and it ran like complete garbage (just like it had a carb problem) until I had the power valve adjusted properly. Of course, RMs have a different set up--the power valve is designed to be adjustable.